Mortar composition and structures incorporating such compositions



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- 3,470,004 MORTAR COMPOSITION AND STRUCTURES INCORPORATING SUCHCOMPOSITIONS Edward R. Begley and Robert F. Patrick, Louisville, Ky.,

and Thomas M. Wehrenberg, Jefl'ersonville, Ind., as-

begin to wear thin towards the end of their useful life, due to poorbonding of existing mortars on the market.

United States Patent filler particles are added to provide Such mortarsadhere or bond poorly to fused-cast brick or re-bonded fused grainbrick. The proposed mortar wets and bonds such bodies very strongly,e.g. the modulus of rupture joint bonding strength is on the order of1000- 2000 p.s.i.

signers to Corhart Refractories Company, Louisville, 5 Accordingly. a py object of the presentinvention Ky., a corporation of Delaware is toprovide a mortar composition which will permit im- No Drawing. FiledNov. 22, 1966, Ser. No. 596,079 proved bonding of fused-cast bricks,especially of the Int (1 C04!) 35/ 35/42. 35/20 chrome-magnesia type. Acollateral object of the inven- 106-59 7 Claims tion is to providestructures of improved life and corro- 10 sion resistance comprising aplurality of refractory articles bonded by a mortar composition.ABSTRACT OF THE DISCLOSURE According to the present invention, there isprovided A composition suitable for preparing a refractory a mortarcomposition comprising the following congnortar comprising from 78 to92% of fused-cast refracstituents: tory particles conmisipg chrome oreand magnesia having Percent fianicle size of less than about 50 mesh,from JTO/IO% Fused particles of refractory chrome-ma nesia of aplasticizin agent in the form of filler particles, from having aparticle size of less Than 50 mesh 5 m wfiaisolfile sodium silicate andfrom 0.03' to with the major portion being less than 100 0.5% organicwetting agent. mesh 78-92 Plasticizing agent 5-10 Water soluble powderedsodium silicate having a This invention relates to a mortar compositionand Soda to slhca of P m my 1:2 and structures incorporating such acomposition. More par- 9 of approximately 27 percent ticularly, theinvention relates to a refractory mortar comw agent 003-05 position forbonding refractory articles, especially fused- The composition of thefused-cast refractory particles cast refractory chrome magnesia bricksand other bonded employed in this invention broadly and analyticallyconbasic bricks. The invention also is concerned with strucsistsessentially of, by weight, at least 40% MgO and at tures comprising aplurality of refractory articles bonded least one other constituentselected from the gr'oup conby the mortar composition. j 30 sisting of:(1) less than 30% oxide selected from the Refractory bricks are used inthe construction of metgroup consisting of FeO, CaO, BaO, SrO andmixtures allurgical furnaces and the like. It is important that thethereof, (2) up to 58% cl'gos, (3) up' to 40% A1 0 resulting structureshave long life, strength, resistance to (4) up to 18% TiO,, (5) not morethan 5% Sit), and (6) corrosion on contact with molten metal and slag,and reup to 7% fluorine, provided that the sum of MgO plus sistance tothermal and mechanical stresses. i the other constituent or constituentsamounts to at least Where direct contact with molten metal and fusedbasic 95% of the particles composition. slag is encountered, basicrefractory bricks are ordinarily For a variety of applications insteelmaking furnaces employed. Typical of such bricks are the fused-castor vessels, copper producing furnaces and cemeiit'producchrome-magnesiarefractory bricks described in US. Pating kilns the composition of theparticles desirably conent 2,599,566, R. I. Magri, In, issued June 10,1952; 40 sists essentially of, by weight, 50 to 70% MgO,-Q1} to 18%2,690,974, R. J. Magri, Jr. issued Oct. 5, 1954; 3,132,954, FeO, notmore than 2% CaO, 10 to 25% Cr O not A. M. Alper et al., issued May 12,1964 and 3,198,643, more than 15% A1 0 not more than 5% TiO not A. M.Alper et a1. issued Aug. 3, 1965; and application more than 5% SiO, andnot more than 2% fluorine, pro- Ser. No. 435,083 filed Feb. 24, 1965 inthe names of R. F. vided the sum of these named constituents is at least95%. Patrick and T. M; Wehrenberg. All of the cited patents and Forcertain special applications, as in basic oxygen the pending applicationare assigned to the assignee of the steelmaking vessels utilizing highlime-silica ratio slags, present invention. the composition of therefractory particles desirably con- In using the basic fused-castchrome-magnesia refracsists essentially of, by weight, at least 75% MgO,not more tory bricks which are the subject of the above patents, than 5%oxide selected from the group consisting of FeO, it has been found thatavailable mortar compositions have CaO, BaO, SrO and mixtures thereof,not more than 15 been generally unsatisfactory. The problem stems inpart Cr O and 5 to 15% TiO,, provided the sum of these from the factthat it is more difiicult to make a fusednamed constituents is at least95%. cast brick to a particular size than it is to produce a The fusedfines are prepared by melting the necessary pressed and fired brick todesired specifications. Improved ingredients to form a composition ofthe above analysis, dimensions can be obtained by diamond grinding, butthis solidifying the melt and comminuting the solid to prois expensive.As a result, the fused-cast bricks vary more vide fines of less than 50mesh. Raw materials suited to in dimensions than do conventionalrefractory bricks. produce fines of the above compositions are fully setforth Therefore, it is more difiicult to get tight joints with fusedinthe above-referenced patents. cast bricks than with pressed bricks.Since the joints in A preferred composition of the fused particlesconsists a structure made with fused-cast bricks are more openessentially of, analytically, on a percent by weight basis, and lessregular in size, more mortar is required to fill about 56.7% MgO, 20.0%Cr O 9.0% A1 0 10.0% the gaps between the bricks. Also, since the mortaris nor- FeO, 0.5% CaO, 1.0% TiO 2.5% SiO, and 0.3% mally less resistantto corrosion than the bricks, the wider fluorine. gaps in fused-castbrick installations offer more vulner- It may be possible to reduce thecost of the above mortar able points for attack by molten metal and slagand make composition by including minor amounts of calcined the mortarcomposition a much more critical factor in magnesia and/or chrome orewithout losing all the benefits achieving long service life. Anotherproblem arising, from gained from using the fused grain. the widerdimensional tolerances of fused-cast bricks of As a plasticizing agent,there is preferably employed a the present type is that it is moredifficult to maintain kaolin, such as Florida kaolin, havingaparticlesize of less the structural integrity of an installation when the bricksthan 40 microns and containing 39% A1 0,. The inorganic desiredworkability and plasticity properties.

Other plasticizing agents which might be used in the composition includeorganic materials such as methyl cellulose or polyethylene glycol,(Carbowax) and inorganic materials such as bentonite clays, etc., butthe Florida kaolin, mentioned above is preferred.

A concentrated organic wetting agent is employed in the composition toeffect a smaller requirement of water and thereby reduce dryingshrinkage to a minimum. A sodium dioctyl sulfosuccinate wetting agent isa preferred material, but other wetting agents may also be employed toreduce the amount of water necessary and to improve the wettability ofthe solid particles.

The dry materials are thoroughly mixed in a blender and are ready forsale and shipment in that condition. At the point of use, suflicientwater is added to form a plastic composition of a consistency such thatit can be troweled or dipped and otherwise used as are conventionalmortars. Approximately 14% by weight of water, thoroughly blended withthe dried powder mix, is sulficient to provide the desired consistency.The quantity of water may be varied depending upon the individual masonspreference, whether vertical or bed joints are being made, etc.

In bonding bricks together, the mortar is applied in conventionalfashion. The water from the mortar is absorbed by the brick surfaces andcarries small amounts of sodium silicate and fine particles of the fusedrefractory chrome-magnesia into the pores of the surfaces being bonded.On drying, a bonding strength of approximately 1000 p.s.i.(ASTM-C199-97, modified) is achieved with fused-cast chrome-magnesiabricks and other direct bonded basic bricks.

As the temperature of a structure incorporating the present mortar israised during use, the hydraulic bond begins to fail at intermediatetemperatures and a ceramic escaping from mortared joints when burning inis re duced considerably.

(2) Drying and firing shrinkage is very low due to high solids contentand small amount of water required for mixing. The present mortar doesnot overfire or bloat at high temperatures.

(3) Minimum silicates reduces brick penetration so that the mortar. doesnot alter brick properties.

(4) Good bonding strength is maintained at all temperatures.

The invention will be more fully appreciated in the light of thefollowing detailed example.

Example The following dry powders were mixed in the indicated amounts byweight:

Percent Fused chrome-magnesia particles having a size of less than 50mesh, the major portion of which is less than 100 mesh 80 Florida kaolinhaving a particle size of less than 4.0

microns Aerosol OT wetting agent 0.5 Sodium silicate 9.5

rather t The fused chrome-magnesia particles had the followingcomposition, analytically, on a percent by weight basis:

Percent MgQ 56.7 CF20} A1 0 9.0 FeO 10.0 CaO 0.5 TiO, 1.0 SiO, 2.5Fluorine 0.3

Mortar A-A wet, air-set, high alumina content mortar. Mortar BA dry,air-set, magnesite mortar.

Mortar C-A dry, heat-set, extra-high alumina content mortar. Mortar D-Adry, air-set magnesite (periclase) mortar. Mortar EA dry, air-setmagnesite (periclase) mortar.

(2) Other structures were prepared using the present mortar and theabove-named commercially available mortars A-E applied to re-bondedfused grain bricks. The bricks had the same composition as the fusedchromemagnesia particles used in the mortar of the present invention.

(3) Other structures were also prepared using commercially availabledirect bonded chrome-magnesite bricks, some bonded with the mortar ofthe invention and others with the commercially available mortars A-E.

The structures were cured at temperatures of C., 400 C., 800 C., 1200C., and 1600 C. After curing at each temperature, the bonding strength,i.e. modulus of rupture at the joints, in pounds per square inch, wasmeasured according to the ASTM test designation C-199- 47, modified. Theresults of the tests are reported in the following table.

TABLE-MORTAR TEST COMPARISON [Bonding strength, modulus of rupture(oint) p.s.i. ASTM designation: C-199-47, mo ifledl F d gut-ing Mortarchr rii eemp. m n in o. A B 0 D E fiof sr (1) Fused cast brick 1,185 1,099 N S NS 131 227 2, 365 2,521 NS NS NS NS 823 1, 692 N S NS N 8 NS 7141, 334 144 NS 78 NS 1, 074

(2) Rebonded fused grain brick 2,000 NS NS 226 94 774 2,810 NS NS 163 NS1, 448 1,209 NS NS NS NS 796 1, 650 NS NS N S NS 832 l 290 NS NS 49 3021, 405 (3) Direct-bonded chrome magnesite brick 2, 419 NS NS 234 NS1,327 2, 090 N S N 8 NS NS 873 1, 818 205 NS NS NS 826 1, 756 61 637 248N S 779 1, 392 NS 1, 215 41 452 1, 173

l The high alkaline silicate mortar completely vitrified at thistemperature, and ran from the ioints or was absorbed by the brick.Weight of top brick closed joint bringing brick feces into contact witheach other.

9 Actual bonding to the fused cast brick was poor. Joint strength camefrom iargueipores on the sample lace filled with mortar yieldingmechanical n bonding strength. NS (no strength) indicates t at the bondevidenced "very low strength, below 20 p.s.i., which is the lowest valuemeasurable on test machine.

It will be seen from the above that very high strength bonding isachieved between fused cast magnesia and basic bricks by use of thepresent mortar through all temperature ranges. The resulting structureshave a minimum bonding strength at the joints in excess of 700 psi, fromroom temperature to 1600 C. The commercially available mortars eitherfail to have adequate continuous bonding strength throughout therequired temperature range or have very poor refractoriness at hightemperatures.

It will be appreciated that the invention is not limited to the specificdetails set forth in the examples and il lustrations, except insofar asis specified in the claims, and that various changes or modifications tomeet individual whim or particular need may be made to obtain all orpart of the benefits of this invention without departing from thereasonable spirit and scope of the claims therefor.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. A dry powder composition which upon admixture with water provides animproved refractory mortar com-= position consisting essentially of,analytically, on a percent by weight basis, (A) from 78 to 92% offused-cast refractory .particles consisting essentially of, by weight onan analytic basis: (1) at least 40% MgO and at least one otherconstituent selected from the group consisting of: (a) less than 30% ofan oxide selected from the group consisting of FeO, CaO, BaO, SrO, andmixtures thereof, (b) up to 58% Cr O (c) up to 40% A1 (d) up to 18% TiO(e) up to 5% SiO-,, and (f) up to 7% fluorine, (2) the sum of MgO plusthe other constituents amounting to at least 95% of the composition offusedcast refractory particles, having a particle size of less thanabout 50 mesh, the majority of which is less than 100 mesh, (B) from 5to 10% of a plasticizing agent, (C) from 5 to 10% water soluble sodiumsilicate, and (D) from 0.03 to 0.5% organic wetting agent.

2. The mortar composition of claim 1 wherein the plasticizing agentcomprises kaolin.

3. The composition of claim 1 wherein the water soluble sodium silicatehas a soda to silica ratio of approximately 1:2 and a Na O content ofapproximately 27%.

4. The mortar composition of claim 2 wherein the kaolin is in the formof particles having a particle size of less than about 40 microns.

5. A mortar composition consisting essentially of a mixture of a drypowder composition consisting essentially of, analytically, on a percentby weight basis, (A) from 78 to 92% of fused-cast refractory particlesconsisting essentially of, by weight, on an analytic basis: (1) at least40% MgO and at least one other constituent selected from the groupconsisting of: (a) less than 30% of an oxide selected from the groupconsisting of FeO, CaO, BaO, SrO, and mixtures thereof, (b) up to 58% CrO (c) up to 40% A1 0 (d) up to 18% TiO (e) up to 5% SiO;, and (f) up to7% fluorine, (2) the sum of MgO plus the other constituents amounting toat least 95% of the composition of fused-cast refractory particles,having a particle size of less than about 50 mesh, the majority of whichless than mesh, (B) from 5 to 10% of a plasticizing agent, (C) from 5 to10% water soluble sodium silicate, and (D) from 0.03 to 0.5% organicwetting agent and sufficient water to provide a workable plastic mass.

6. The mortar composition of claim 5 wherein the plasticizing agentcomprises kaolin.

7. The mortar composition of claim 6 wherein the kaolin is in the formof particles having a particle size of less than about 40 microns.

, References Cited UNITED STATES PATENTS 3,145,188 8/1964 Martinet et a]106-59 3,208,862 9/1965 Davies et al. 106-84 3,297,457 1/ 1967 Charvat106-59 JAMES E. POER, Primary Examiner US. Cl. X.R. 106-84

